Litigation and science may determine where the NCAA goes from here. The NCAA requires a concussion management plan from each school but doesn't enforce it. Also, two Division I conferences now have stricter practice restrictions in football than the NCAA's guidelines.

"League of Denial" focuses in part on Boston University neuropathologist Ann McKee, who has studied the brains of 46 ex-NFL players and found chronic traumatic encephalopathy (CTE) in 45 of them, plus evidence in one high school and one college player. CTE is a degenerative brain disease associated with head trauma.

While acknowledging the study's sample size is small so far, McKee told Frontline, "I'm really wondering if at some level every single football player has this."

Hainline, a neurologist who became the NCAA's top medical official in January, said he believes there is "evolving evidence" that multiple head injuries in football can be linked to brain injuries, such as CTE. However, he said there is no data to prove that athletes who suffer concussions are more susceptible to longterm brain injuries.

"I think the overwhelming majority of athletes who have a concussion, they recover from a concussion," Hainline said. "I think there's a subgroup of athletes who either have a genetic susceptibility or they have repeated concussions or subconcussions and the brain has not gone into recovery mode and they become susceptible to longterm brain issues."

Brian Hainline has been the NCAA's chief medical officer since January. (Photo from NCAA.org)

Hainline cautioned that there are many people who suffer from Alzheimer's, Parkinson's and Lou Gehrig's diseases yet never experienced head trauma. CTE has features of those diseases but the science is evolving, he said. Theories such as genetics, drug use, stimulants and psychiatric disease are "very possible reasons" some players absorb subconcussive impacts worse than others, Hainline said.

Hainline noted that he is working behind the scenes on research with Robert Stern, a neurologist at Boston University. Stern was featured in "League of Denial" and said on the program that a critical question is why one person gets CTE and another person doesn't.

"I think there's enough evidence out there that we have to take this seriously," Hainline said. "The mechanism (that causes CTE), that's what's stupefying."

Repeated blows to the head

College football is tackling the so-called "kill shots" in the game with this year's new ejection rule for targeting. What leaders collectively haven't done is determine what, if anything, can or should be done about the repeated blows to the head football players experience through subconcussive hits.

The Pac-12 joined the Ivy League this year in placing full-contact restrictions at twice a week. The NCAA maximum is five per week, although many coaches have said they limit their full-contact practices to two or three a week.

"I think there's going to be a point where there's a uniform guideline," Hainline said. "Is it going to be a legislative issue or a guideline? Right now, I don't know the answer to that. It's probably going to evolve initially as a guideline."

The NCAA typically focuses on issues such as amateurism so this is a "new way" for the NCAA to think about what it governs, Hainline said. The NCAA Concussion Task Force plans to work on a data analysis of Ivy League and Pac-12 practice restrictions.

"Unfortunately, we don't have the data analysis of the Ivy League yet and the Pac-12 is just on the verge of getting data," Hainline said.

Ivy League Executive Director Robin Harris, whose league adopted practice restrictions in 2011, said the NCAA has its football practice report. The Ivy League has told the NCAA it can't necessarily provide a short-term answer on whether practice limits reduce concussions, Harris said.

She said comparing data from two or three years ago may not make sense because the attention on concussions likely caused athletes to report more concussion symptoms. She believes more athletes will report concussions in the future.

"We did this because it makes sense, and in the absence of anything else, we cannot afford to wait for limits," Harris said. "I can't tell you it's the panacea for all issues or that there's a cause and effect. It was one of the steps to try to address it proactively. It's frustrating that others haven't followed suit because they don't have data. I'm pleased the Pac-12 has followed our league."

Because of how the NCAA is structured, the membership would have to create practice limits, not the NCAA staff, Harris said.

"The committees that look at this don't want to make changes until they have specific data saying practice restrictions have this effect," she said. "We can't tell them and won't have that for years."

NCAA supports 'Heads Up' approach

Hainline defended the NCAA's approach by saying there is no uniformity across all of football over practice limits. He noted that youth football's major organizations -- USA Football, Pop Warner and American Youth Football -- don't have uniform policies and said the National Federation of State High School Associations offers guidelines that aren't enforceable in every state.

College football will likely be closer to an agreement on practice limits after this season once there's more data, Hainline said.

"One way is to say let's just put out a guideline and go from there," he said. "Another point of view is let's make sure when we really put out this guideline that it addresses the qualitative aspect."

The Pac-12 defines full contact as "any live tackling, live tackling drills, scrimmages or other activities where players are generally taken to the ground." That means thud tackling -- in which players don't bring a teammate to the ground -- is not considered full contact.

Hainline said the Pac-12's definition of full contact is the NCAA's working concept but not accepted by everyone.

"I've been going to a number of football practices," he said. "There's even a difference qualitatively when you have someone taken to the ground at one school compared to another school. That definition may be as close as we can get."

Hainline strongly supports the approach by USA Football, which launched a national "Heads Up" campaign on tackling methods to keep the brain safer. USA Football has seen youth participation drop from 3 million players in 2011 to 2.82 million last year. The organization receives funding and promotion from the NFL.

"I think the real answer is going to be on the nature of practices, the nature of technique and really avoiding the head impact when you don't need to have any," Hainline said. "Then it really needs to be measured as well with the right sensors."

Recognized brain trauma expert Stefan Duma tests helmet impact at Virginia Tech. For the past decade, Virginia Tech players have had sensors in their helmet that measures the number of hits they take and the severity of them. (Photo courtesy of Virginia Tech)

A recent study by Stefan Duma, a brain trauma researcher from the Virginia Tech-Wake Forest School of Biomedical Engineering and Sciences, concluded youth football players are not more susceptible to head hits during games if they had fewer live hitting drills at practices.

"This is a very evolving concept that if you focus on the technique, you don't need to go through all of the drills, and in the long run you're probably going to be reducing the subconcussive impacts in practice," Hainline said. "I don't think it's a completely data-driven process, but I agree with that concept."

Former UCLA linebacker Patrick Larimore has been fighting to change the concussion culture among players, an issue that concerns NCAA chief medical officer Brian Hainline after a recent study. (The Associated Press)

In a paper published in August by the Neurology Clinical Practice, 43 percent of surveyed college athletes with a history of concussions reported they had knowingly hidden symptoms to stay in a game. Also, 22 percent indicated they would be unlikely or very unlikely to report concussion symptoms to a coach or athletic trainer in the future.

"This is perhaps one of my biggest concerns and caught me a little off guard: the effectiveness of our educational outreach," Hainline said. "Even if somebody is very knowledgable of the situation, it doesn't mean behavior is going to change."

Hainline said the NCAA is now tracking how many of its monthly electronic Sports Science Institute newsletters are being opened and forwarded. The newsletter provides health and research information to every NCAA athletic trainer, coach, team physician, and conference commissioner, among others.

Hainline wants to use coaches to help educate players. He is piloting a Division II coaches education program with the Centers for Disease Control and Prevention and U.S. Anti-Doping Agency. The program's theory is a coach is the main influence on a young athlete's life, and will focus on education related to doping, supplements and concussions.

"I'm cautiously optimistic we're going to start having an impact that way," Hainline said. "I'm not naive about education. I spent my life in that field."

Hainline said the NCAA is focused on future research as well. On the day damaging information was filed in the Adrian Arrington lawsuit against the NCAA -- the two parties are scheduled for mediation next month -- the NCAA announced a $399,999 grant to study the longterm health of concussed college athletes from more than 10 years ago.

The NCAA wants to find a helmet senor that measures rotational acceleration forces on hits. Hainline thinks science is two years away from meaningful genetic biomarkers -- through MRIs and blood tests -- to evaluate an athlete's predisposition to concussions. Also, Hainline is intrigued by researching the brain's electrical activity to distinguish a concussion from a subconcussion.

As parents consider whether to let their kids play football, Hainline said he hopes the sport has a much different culture 10 years from now.

"I happen to really buy into the philosophy with USA Football's 'Heads-Up' program, and as a society we say there are a lot of sports that have inherent risks, certainly not just football," he said. "If we as a society say, yes, we accept some risk from contact sports but we won't accept a culture that places unnecessary risks, I think we'll see a football that looks a little different but essentially a sport that's still following its rules."